Method and apparatus for controlling the linear velocity between an optical head and a rotation disk

Abstract

An improved method and apparatus for maintaining a recording head in an optical recording system at a constant linear velocity relative to a rotatable disk support. A rotation controller uses a cumulative measure of rotation to determine an angular velocity of the rotating disk support necessary to maintain a constant linear velocity.

I claim: 
     
       1. An improvement in an optical recording system comprising an optical recording head, a rotatable disk support positioned in close proximity to the optical recording head and movable along a first path comprising a radial component and starting at an initial radial position, a translation motor for moving the rotatable disk support, a disk motor coupled to the disk support to rotate the disk support at a selectable angular velocity, a motion sensor coupled to the disk support and operative to generate a sensor signal indicative of rotation of the disk support, a translation controller operative to move the disk support along the first path, the improvement comprising: a rotation controller responsive to the sensor signal and operative to determine a cumulative measure of rotation and to set the disk motor angular velocity as a function of the cumulative measure of rotation to maintain a selected linear velocity between the recording head and the rotating disk.   
     
     
       2. The improvement in claim 1: wherein the sensor signal comprises a plurality of pulses;   wherein a cumulative number of the plurality of pulses is indicative of a rotational displacement of the disk support; and   wherein the rotation controller comprises a first pulse counter responsive to the pulses.   
     
     
       3. The improvement in claim 2 wherein the rotation controller further comprises: a pitch input for receiving a selected track pitch;   means for generating a count indicator signal upon receiving a fixed number of the plurality of pulses; and   rotation determining means for determining the cumulative measure of rotation in response to the count indicator signal is generated, the cumulative measure of rotation determined as a function of the selected track pitch.   
     
     
       4. The improvement in claim 1 wherein the rotation controller comprises a phase-locked loop frequency synthesizer for generating a rotation control signal indicative of the disk motor angular velocity, the rotation control signal determined according to the cumulative measure of rotation and the selected linear velocity. 
     
     
       5. The improvement in claim 1 wherein the rotation controller comprises a frequency generator for generating a rotation control signal indicative of the disk motor angular velocity, the rotation control signal determined according to the cumulative measure of rotation and the selected linear velocity. 
     
     
       6. An improvement in an optical recording system comprising a rotatable disk support, an optical recording head positioned in close proximity to the rotatable disk support and movable along a first path comprising a radial component and starting at an initial radial position, a translation motor for moving the optical recording head, a disk motor coupled to the disk support to rotate the disk support at a selectable angular velocity, a motion sensor coupled to the disk support and operative to generate a sensor signal indicative of rotation of the disk support, the improvement comprising: a translation controller operative to move the recording head along the first path; and   a rotation controller responsive to the sensor signal and operative to determine a cumulative measure of rotation and to set the disk motor angular velocity as a function of the cumulative measure of rotation to maintain a selected linear velocity between the recording head and the rotating disk.   
     
     
       7. The improvement in claim 6: wherein the sensor signal comprises a plurality of pulses;   wherein a cumulative number of the plurality of pulses is indicative of a rotational displacement of the disk support; and   wherein the rotation controller comprises a first pulse counter responsive to the pulses.   
     
     
       8. The improvement in claim 7 wherein the rotation controller further comprises: a pitch input for receiving a selected track pitch;   means for generating a count indicator signal upon receiving a fixed number of the plurality of pulses; and   rotation determining means for determining the cumulative measure of rotation in response to the count indicator signal is generated, the cumulative measure of rotation determined as a function of the selected track pitch.   
     
     
       9. The improvement in claim 6 wherein the rotation controller comprises a phase-locked loop frequency synthesizer for generating a rotation control signal indicative of the disk motor angular velocity, the rotation control signal determined according to the cumulative measure of rotation and the selected linear velocity. 
     
     
       10. The improvement in claim 6 wherein the rotation controller comprises a frequency generator for generating a rotation control signal indicative of the disk motor angular velocity, the rotation control signal determined according to the cumulative measure of rotation and the selected linear velocity. 
     
     
       11. In an optical recording system, a method for maintaining a radially movable and rotatable disk at a constant linear velocity relative to an optical recording head, the method comprising the steps of: generating a translation of the optical recording head relative to the rotatable disk support, the translation starting from an initial radial position along a radial path;   rotating the rotatable disk at an initial angular velocity;   determining a cumulative measure of rotation of the rotating disk; and   updating the angular velocity of the rotating disk in response to the cumulative measure of rotation to maintain the constant linear velocity.   
     
     
       12. The method of claim 11 wherein the step of determining the cumulative measure of rotation comprises the steps of: generating pulses in response to the rotation of the rotatable disk;   counting the pulses; and   maintaining a pulse count; and   wherein the step of determining the cumulative measure of rotation is responsive to the pulse count.   
     
     
       13. The method of claim 11 wherein the step of determining the cumulative measure of rotation further comprises the step of: generating a count indicator signal each time a fixed number of pulses is counted; and   determining a cumulative measure of rotation by retrieving a cumulative pulse count each time a count indicator signal is generated.   
     
     
       14. The method of claim 11 wherein the step of generating a translation further comprises the step of: moving the rotatable disk support in a linear direction relative to the stationary optical recording head.   
     
     
       15. The method of claim 11 wherein the step of: moving the optical recording head in a linear direction relative to the stationary rotatable disk support.